Question: $\dfrac{3}{12} - \dfrac{5}{4} = {?}$
Answer: $ = {\dfrac{3 \times 1}{12 \times 1}} - {\dfrac{5 \times 3}{4 \times 3}} $ $ = {\dfrac{3}{12}} - {\dfrac{15}{12}} $ $ = \dfrac{{3} - {15}}{12} $ $ = -\dfrac{12}{12}$